Destruction by shock waves of insect life in infested products



Mardi 5, 1957 F. s. sMn-H DESTRUCTION BY SHOCK WAVES OF INSECTv LFE IN INFESTED PRODUCTS Filed D86. 29, 1953 .sa 567A BL h f7 in L am 2 w ,/6 \.l RY m 7 my 35 e f y* i United States Patent QC, 285,337,652

Figure El is an end elevation as seenv from the right in Figure`2; Figure 4 is a view, partly in transverse 'vertical sec- 2,783,760

DESTRUCTION BY SHOCK WAVFS 0F lNSECT LIFE IN INFESTED PRODUCTS This invention relates to a method and apparatus for treating insect-infested products by shock waves for the tion, of a'treatment zone or chamber, certain parts being diagrammatically indicated, illustrating one possible form or embodiment thereof and in association with a moving product where the latter is moved by avconveyor belt; and I .v j

Figure 5 is a frontelevatiompartly in central ver- 0 .tical section, of a treatment zone or chamber, certain destruction of such insect life in its various forms or I other object is to provide a method and apparatus'of the above nature that is well adapted to meet varying or different requirements met with in practice. Another object is to provide a method and apparatus of the above nature inwhich the subjection to shock waves of the product may be effectively carried on in such continuity as will facilitate incorporation of the apparatus and the practice of the methodl into the usually continuous and substantially uninterruted flow or travel vof the infested product, as in a production line or stream. Another object is to provide, in apparatus of the above-mentioned character, a shock-wave-producing and product-treatment zone or chamber capable of ready adaptability or association with the factory equipment operating in the .production or processing or utilization of the product and capable of shock wave treatment of the product at a rate or capacity commensurate with that of the factory equipment. Another object is to carry out this last mentioned object by shock-wave-producing means constructed and operating so that it or multiples thereof can be dependably arranged or disposed relative to the treatment zone and more particularly relative to the lcharacteristic of distribution or ow or travel of the product to be treated. Another object is to provide, in apparatus of the above character, ease and dependability of control of rate and intensity of shock wave production so as to readily suit the apparatus to characteristics of the product to be treated, characteristics 'of the treatment zone or chamber, or characteristics of the insect infestaeach of the same to one or more of the others, .all as will be illustratively described herein, and the scope ofthe application of which will be indicated in the following claims.

In the accompanying drawings in which are shown various possible embodiments of the mechanical features of my invention,

Figure l is a representation of my apparatusfor continuous treatment, by shock waves, of a product, the treatment zone or chamber being only schematically indicated and a preferredand illustrative form of electrical devices and circuit arrangements, foi shock wave production in the treatment zone or chamber, being diagrammatically shown, together with certain controls therefor;

Figure 2 is a front elevation, on an enlarged scale, of a rotatable circuit-controlling device of Figure l, showing a preferred form of construction thereof;

partsbeing diagrammatically indicated, illustrating another possible form or embodiment thereof, as for example, for association with a conduit along and within which the product is. moved, as from one part of an equipment to another or as in a factory production line. l

Similarreference characters refer to similar parts throughout the several views of the drawing.

yReferring first to Figure 1, the broken line box identi fied by the reference character Z represents schematically` the treatment zone or chamber in lwhich the product,

infested with forms of insect life,' is subjected to insectlife-destroying action of shock waves which are produced by means and infa manner to make practicable and eficient treatmentof also loose products, products made up of particles or many-componentl parts namely in bulk as distinguished from a packaged product, vas well as in a manner -to greatly facilitate association of the shock-wave-producing means with the path of ow or movement of such products in course of productionor processing or utilization thereof, as in aproductio'n machine or as in aline of factory equipment handling such product. Without intending to limit my invention thereto, cut tobacco, such as cigarette tobacco, containing insect infestation, maybe considered as such a product 'for purposes of an illustrative'application of my method and apparatus for destruction by shock waves of forms of insect life and to illustrate ready incorporation of my method and associated means into the line of `liow or movement of the cigarette tobacco in course of machine-production of cigarettes. v

The manner in which the infested product is supported, or carried, or guided, by suitable means, in relation to the zone Z may vary, and in Figure 1 such means is diagrammatically indicated by the reference character C. The shock-wave-producing means comprise preferably a plurality of preferably -high-intensity spark-gaps, diagrammatically indicated at G1 and G2 -in Figure l, with associated energizing and control means as is illustratively about to be described; they are adapted individually,upon spark-over, tov produce in air a shock wave or discontinuity that travels at a lvelocity equal to or `greater than the `local sonic velocity. fThe term local sonic velocity is employed because, while the velocity of sound at sea level and under normal atmospheric pressure and at 20 C. is,l as isknown 1,120 feet per second, it variesprimarily. with change in temperature, that is, generally speaking, increase in temperature of the air increasesthe velocity of' sound, and vice versa. These spark-gaps are preferably controlled and actuated in suitable sequence, also as is about to beiillustratively described, in order to/appropriately correlate distribution vof life-destroying shock waves to area .of exposedv product or rate of movement or carriage or guidance or distribution of the product; in this latter connection,

t according to certain features of my invention, wide ilexibility of arrangement and of functioning are possible and thus dependable life-destroying treatmentrof the infested product made possible and ready adaptability to spark-gaps G1 and G2 are shown, and, upon appropriate energization, preferably at high-intensity current pulses, produce for each spark-over, of which there is one for each current pulse, a shock wave in air of `high intensity, propagated at velocity in excess of the local velocity of sound; each shock wave or shock front carries or travels, with or without guidance or reflective direction, into the infested product brought into the treatment zone Z by the means C. The substantial amount of elec'- trical energy of each spark-over between electrodes creates a severe pressure disturbance or discontinuity in the air which travels at a velocity in excess of the local velocity of sound; the shock wave thus produced is not periodic and its effects are violent because, among other reasons, the air particles are enormously accelerated. In these and other respects, it is dilferent and distinguished from sound waves which are periodic and which always have a definite speed, namely, the speed of sound. It has been discovered that these intense shock waves in air are lethal to all forms of insect life which infest products of the above mentioned nature, such as cigarette tobacco, and accordingly when the product emerges from the treatment zone Z, it emerges with such insect life therein destroyed and can move on, as by the means C, for further processing, as by being entered directly into the cigarette-making machine, and thereby further` spoilage or damage by such initial infestation prevented.

It is usual, in some cigarette-production ylines or machines, to convey the mixed or blended or otherwise prepared cut cigarette tobacco conveyed thereto by means of a conveyor belt and in one illustrative embodiment of my invention I utilize that conveyor belt as the means v C of Figure l and suitably relate thereto shockwaveproducing spark-gap means to subject the travelling tobacco to the lethal action of the shock waves, in a manner llustratively showny in Figure 4 in which is shown a conveyor belt C1 having its upper reach carried by troughing idlers and its lower or return reach carried by return idlers 11, as illustrative of such a cigarette-tobacco conveyor belt mechanism or arrangelent. The conveyor belt C1 is controllably driven in any usual manner by means not shown and on its upper troughed reach it supports the cigarette tobacco P usual ly more or less uniformly distributed thereon both crosswise and lengthwise of the belt for effecting, for a given rate of drive of the belt, more or lless uniform rate of supply of tobacco to and for the cigarette-making or other processing mechanism.

At a suitable location lengthwise of the carrier C1, I provide a suitable number of shock-wave-producing spark-gaps, utilizing preferably spherical electrodes, and arrange them in overlying and spaced relation to the conveyor belt C1 and the layer of product P carried thereby, by insulatingly supporting them by any suitable insulators or insulating support diagrammatically indicated at 12; the insulating means 12 may have associated with it a housing-like structure diagrammaticaily indicated at 14, preferably of conductive material such as sheet metal, being provided with a top `wall l5 which can carry the insulating supports 12 and with opposed side walls 16-17 which, at their lower ends, terminate in proximity to the longitudinal side edges of the carrier belt C1, and with opposed end walls 18-19 that extend transversely of the conveyor belt and terminate in parallel edges above the conveyor belt. The structure 14, being thus given a somewhat hood-like form with the Qark-gap electrodes projecting downwardly into it from Il top wall 15, forms with the moving conveyor belt C1 a treatment chamber or zone in which the continuously moving tobacco P is subjected to the insect-life-destroying action of the shock waves which are produced by and propagated from the spark-gaps in a repetitive and preferably also successive or sequential manner about to be As above noted I preferably employ a plurality of thereof for sequential shock wave production.

spark-gaps and to simplify the drawing and explanation of these features of my invention, I have shown in Figure l two spark-gaps G1 and G2 with an energizing and control system therefor which illustrates how two or more shock-wave-producing spark-gaps may be related to the particular characteristics of the means C of Figure l and the product distribution thereon or movement thereby, together with correlated sequential energization For example, let it be assumed that, in connection with the above described treatment zone of Figure 4 utilizing the conveyor belt C1, the conveyor belt is of a width in relation to the shock-waveproducing characteristics of the spark-gap employed such that it is desirable or necessary to employ two spark-gaps spaced transversely of the belt C1, as is diagrammatically indicated in Figure 4 by the two spark-gaps G1 and G2 whose respective spherical electrodes lil-E"i and EI--EL are shown substantially aligned transversely of the conveyor belt C1 so that spark-gap Gl more or less overlies the left half of the belt and spark-gap G2 more or less overlies the right half of the belt. Were the conveyor belt Cl to bewider than that assumed in the illustration, more than two spark-gaps would be so aligned transversely of the belt as will now be clear. Accordingly where more than one shock-wave-producing spark-gap is employed in order to adequately cover the width of the belt and the width of the spread of the product P thereon, l preferably arrange for the sequential energization of these sparkgaps in direction transversely `of the belt and such energization I can adequately illustrate by the use of two transversely disposed spark-gaps as in Figure 4.

As a source of energy to effect appropriate intense spark discharge between the electrodes of the sparkgaps to produce intense shock waves in air at the spark gaps, I prefer to employ a condenser 20 of suitable capacity and voltage to effect suitably intense spark discharge across the spark-gap or spark-gaps preferably by way of controls later described; the condenser 20V is connected to a suitable source of high voltage unidirectional electrical energy for charging it, and in Figure l an illustrative arrangement for charging the condenser is shown. Thus, I may utilize, a source of S-phase alternating current energy such as a factory B-phase power,

line indicated by the reference characters L1, L, and L3 and by way of a switch 2l I may connect thereto the low voltage or primaryrwindings of a step-up transformer generally indicated by the reference character T; transformer T may be `of any suitable iron core construction and llustratively its primary windings may be delta-connected and Aits secondary or high voltage windings may be star-connected, as indicated in Figure l. lts high voltage output is rectified by any suitable means for unidirectionally charging the condenser 20 and in Figure l l have shown a conventional fullwave rectifier arrangement comprising suitable electronic conduction tubes, such as kenotrons 22-23-24 and 25-26-27, interposed between the transformer secondary windings and the condenser 20. The tlamentsof kenotrons 22-23- 24 are energized at suitable low voltage from a phase of the supply circuit L1, L, L3, through an insulating step-down transformer 28, with a switch 30 interposed between the transformer 28 and the power supply line.

In similar manner the filaments of kenotrons 25-26-27 are supplied with heating current from a phase of the 3-phase power supply line, through a switch 31 and an insulating step-down transformer 32. With the resultant circuit connections and arrangement the capacitor 20 is charged unidirectionally to substantially the full secondary voltage of transformer T; llustratively. that may be a voltage on the order of magnitude. of said 40,000 volts.

The several shock-wave-producing spark-gaps, illustratively the two spark-gaps G1 and GS, l connectin parallel,

, positive side of condenser 20.

1 sponding high voltage spark-gapvcircuit takes place.

" through suitable resistances, to the condenser 20 butwiththe circuit ofeach spark-gap individually controlled, each preferably b`y 'an-electronic conduction device of con- ,troilable conductivity by a suitable control element, suchv as a magnetronl in which conductivity between lits cylindrical anode and coaxial iilament or cathode is vcontrollable, as is knownhby the. intensity of the magnetic field of a. coaxial solenoid wind-ing. Accordingly, where there are two spark-gaps G1 and G1 as in Figure l, I employ two magnetrons generally indicated by the reference char- A acters M1-and M2, one for each of the spark-gaps.

I provide suitable means for heating the filament cath- -odes of the magnetrons .M1 and M2 at suitable low voltage; for example, their respective filaments F1 and F11 are connected in parallel as shown, to the low voltagewinding,'by conductors 34--35,`ol:' an 4insulating step-down -transformer 436 whose primary winding `is connected through a switch 37 to one phase of the power supply line L1, L2, L3. Any suitable means may be employed to vary at will the energizing current supplied to theV magnetron filaments, such as suitable taps 38 associated-f wthawinding of the transformer 36 or, by way of fur- 4ther illustration, by individual variable resistances 40 and '41 in the respective parallel circuits ,ofthe filaments F1 the shaft 63 of the timer-distributor D drives the latter at suitable low speed and preferably the reduction gear 62 is selectably variable or changeable so that anyone of a suitable range of low speeds of drive of the timer-distributor D may be selected, as by a speed-ratio selector diagrammatically indicated at 64.

An illustrative construction of timer-distributor may comprise a cylindrical hub pr support 65 made of suitable solid dielectric material; and adapted in anysuitable way to be coaxially` mounted and secured to thkdrive shaftv 63; this insulating hub 65 carries, on its external cylindrical surface, a conductive sleeve 66 securely atixed thereto, as by a shrink-tit or otherwise, and it presents. an external cylindrical surface with which' a suitable number of current-interrupters and external stationary brushes coact, according to the number of shock-wave-'producing spark-gaps that are to be sequentiallyactivated throughv a corresponding number of electronic valves such asr the magnetrons above mentioned. l Accordingly, and by way of the playing ltwo shock-wave-producing spark-'gaps' and two magnetrons, I provide two brushes B1 and/B1, one for each of the two magnetrons M1 and M2, and they, Atogetherv and F1. Byconductor 42 the lamen'tcathodes 'of thel 25 several magnetrons are connected to the negative side of I the condenser 20. v

The'anode A1.of\ magnetron M1 is connected by conduct'or` "43 and a resistor. R1 and conductor 44 to the' negativesphereelectrode E3 of spark-gap G1; the posi- 3Q tive sphere electrode E'1\ of thelatter is ,connected by conductor 45. andA resistor R3 and conductor 46 to the In similar manner,` the 4shock-wave-producing sparkgapl Gfv has' interposed between it and the condenser 20 theconductively controllable valve elements of magnetron M2; with filament F2 of the` latter connected -by conductor 42` tothe negative side` of condenser 20, the

with a third brush B are` insulatingly supported, through theirjconductive brush-holders (see Figures 2 and 3), by Iany suitable form of insulating support diagrammatically `indicated at 68. These brushes may be aligned parallel to the axis of rotation of the conductive sleeve 66 and are spaced axially therealong so that, as the timer-distributor element rotates, the brushes engage with different-peripheral regions of the sleeve 66.l The middle brushvB is connected by conductor 71 (Figure 1) to onefterminal of .the D. C. generator 56. Brush B1 is connected by con-` ductor 7-2 to one terminal of solenoid S1 of magnetron M1 and conductor` 73 connects the other terminal of winding S1 .to the other terminal of D. `C.generatorl56. Confductor 74 connects brush B2 to one endofsolenoid S2 f anode A2 of magnetron M2 is connected by conductor 51 and resistor R2 and conductor S2 to the negative 40 sphere electrode E4 of the spark-gap G2 of which the positive sphere electrode `E2 is connected by conductor 53 and resistor R4 and conductor 54 to the positive side of the capacitor 20.

The electromagnetic or solenoid windings ofi-magnetrons M1 and M2 are diagrammatically indicated at S1 and S2 respectively and, according to certain features of my invention, these I arrangeffor sequentially .controlled jenergization fory corresponding sequential activation, by condenser discharge, of the spark-gaps G1 and G2. These 'solenoids are energized -by unidirectional Vcurrent and when each" produces a magnetieeld above/the critical -valuelfor Athe magnetron construction, conductivity between cathode and anode is substantially reduced to zero o and current inthe high voltage spark-gap circuit cannot how; when the magnetic eld of the solenoid winding is -4 A,phase of the power supply line. ,The dnve of D. C.

generator 56 may thus b'e advantageously at constant speed and motor 57 can thus also provide a uniform rate of drive for'a timer-distributor generally indicated by the reference character D by which energization of the magnetron solengids is controlled. Conveniently, motor 57 may be provided with any suitable form of built-in speedof magnetron M2 and the other terminal .of winding S2 is connected by conductor 73 toy the other terminal of `the generator 56.

The contactor sleeve 66 is provided with two current interrupters 'and 76 made of suitable solid dielectric material and they are spaced apart (see Figure 3) v andare axially displaced (see Figure 2) for coaction respectively with the brushes B1 and B2; conveniently they are in the form of blocks of insulating material of trapezoidal cross-section as shown in Figure 3 and `ittedvand securely held in slots, in the contactor sleeve 66, o'substantially corresponding cross-section. Relative to the brushes with which they respectively coact, each presents' a peripheral face, of thesame radius as the outside radius of contactor sleeve 66, that is of greater dimension'in both axial and peripheral direction (see Figures 2 and 3) than is the contacting face of the brush. 'g -l Brushes B1 and Bare bridged by a resistor R5 and jbrushes B11 and B are bridged by a' resistor'R. Accordingly, as the timer-distributor D is driven at the selected speed,'the magnetrons are made to become-conductive in succession and at tlieselected or desired rate yof succession, thereby co'rrespondingly effectingdischarges of Iintense current pulses from the condenser 20 successively through or across the spark-gaps and where two sparkgaps and two magnetrons are` so employed the shockwave-producing spark discharges acrossl the spark-gaps G1 and G1 occuralternately, that is, in the order'G1, G1,-G1, G1, G1, etc. It will now be clear that, where more than two such 'spark-gaps and corresponding magnetrons are employed, illustratively three, vthe shock wave production, by the respective spark discharges, occurs in repeated sequences or successions as for example in the order G1, G1, X, G1, G1'. X,G1,Ietc., where X is the added spark-gap to make the three; in such case the timerdistributor D is provided with an additional brush and reduction gear, diagrammatically indicated at 62, so that '15 resistor and with an additional current interrupter element, yand the resultant three-current-interrupter elements above illustration emf mesmo are peripherally distributed in ,the contactor sleeve 66 equiangularly and hence at intervals of l20.

The resistors Rs and R0, conveniently connected to the brushes as shown in Figure 2, are alternately cut into and cut out of the circuits of the respective magnetron windings S1 and S2 in order, as will now be clear, to change the magnetic fields of the latter from above the critical value to below the critical value and vice versa. In the position of the parts shown in Figures 1 and 2 resistor R is virtually short-cireuited, through brush B, contactor sleeve 66 and brush B1 and the magnetization of the solenoid S1 is above the critical value and magnetron M1 is non-conductive in tbe circuit of spark-gap G1; on the other hand resistor R, for such time interval as the non-conductive piece or current interrupter 76 is in the contact with brush B2, is in the circuit of solenoid winding S2 so that the magnetic field of the latter is below the -critical value and magnetron M2 is conductive for and during the corresponding time interval, for current-pulse discharge from condenser across sparkgap G2. When the timer-distributor occupies a position 180 displaced from that shown in Figures 2 and 3, current interruptor 75 is contacted by brush B1, resistor R5 is in the solenoid circuit of magnetron M1 so that the latter is conductive for current pulse discharge from condenser Z0 across spark-gap G1, and resistor R8 is cut out of the circuit of solenoid winding S3 so that magnetron M2 is non-conductive and condenser discharge across spark-gap G2 can not take place.

Accordingly it will be seen that by such illustrative. means as above described, the current pulses through each magnetron and hence across each spark-gap are readily fixed to desired values as to pulse period' and duration of pulse. By pulse period is meant the time from one point on a current pulse to the corresponding point on a succeeding current pulse, and thereby the number of shock-wave-producing current pulses, per second, across each spark-gap determined. For each sparkgap the pulse period may be varied by changing the speed of drive of the timer-distributor or by changing the number of current interrupters associated with each magnetron-allocated brush whilemaintaining appropriate phase displacement between the current interrupters coacting with one brush and those coacting with the others. The duration of the pulse is fixed by the time during which the current across each spark-gap is maintained at its maximum value and that is determined by the relative dimensions of the brushes and coacting current interrupters together with the rate of rotary movement of the interrupter elements, for thereby is determined the 'time interval during which the energization of the magnetron solenoid is held at a value of maximum conductivity of the magnetron, exclusive of current build-up and current decay time intervals. These factors, together with suitable current carrying capacity of the magnetrons employed for working filament-temperatures of the latter, are thus readily suited or fixed for shock-waveproducing spark discharge at the spark-gaps, in desired sequences such as those illustratively above described.

At each spark-over, substantial energy is converted into a shock wave or shock front, producing a pressure discontinuity in air that is of high energy content and that is propagated at a velocity greater than the local velocity of sound; with very high energy input into the spark, its velocity may be several times as great as the local velocity of sound and this effect may be accentuated by high rate of energy input into the spark. These shock waves radiate out through an angle of 360 from the path of the intense current pulses across the gap between the electrodes and in radiating out the most intense shock waves move outwardly in a direction non-parallel to the path of the intense current pulses a'cross the gap. It is known that high-intensity sparks are very efficient energy converters in that only a few percent of the electrical energy appears in the form of light and the rest appears essentially as a single pressure pulse in air that is propagated at a velocity greater than the local velocity of sound.

It is such shock waves to which the cigarette tobacco P (s'eeFigure 4) is subjected as it is moved underneath and past the several spark-gaps such as the spark-gaps' G1 and G2 which, as a unit, may be adjusted toward or away from the moving product P, by any suitable means which are diagrammatically indicated simply by doubleheaded arrow 80, as by vertical adjustment of the insulating support 12 relative to the hood structure 14, according to such variables as the thickness or depth of the layer of product P,`the rate of travel thereof, the intensity or strength or range of shock-waves produced at the spark-gaps, or the like, appropriate for providing lethal effect upon the forms of insect life with which the product may be infested. Bv arranging several sparkgaps transversely of the conveyor belt C1 and energizing them in repeated sequences such as those above described, particularly in relation to the travel of the product P as it is moved by the conveyor belt C1, the scope or effective range of the shock waves is readily accommodated to the transverse dimension of the area of distribution of the product P and, in the illustration of Figure 4, to the width of the conveyor belt C1. In like manner shock-wave-producing spark-gaps may be Vgrouped in any other suitable manner relative to the area of distribution of the product or its manner-or rate of movement, and the corresponding plurality of spark-gaps suc-v cessively energized in any suitable sequence of any suitable geometric pattern. For example several aligned shock-wave-producing spark-gaps may be set at a diagonal relative to the pattern of distribution or direction of movement of the product. Or they may be grouped or aligned in the direction of the length of the pattern of distribution or in the direction of travel of the moving product. Thus, though what may be termed the target area covered by the high-pressure high-velocity pulse or shock wave. may be less than the area, or less than a dimension of that area, of exposure of the insectinfested product, I am enabled by suitable relative disposition of a plurality of shockwave-producing sparkgaps and by successively or sequentially energizing them, each at the same pulse period, to effect over-lapping of the individual target areas and thus cover the larger area or larger dimension of the distributed product, and where the product is made to move or travel, illustratively as by the conveyor belt C1 of Figure 4, the resultant movement of the product relative to the geometric pattern' in which the shock-wave-producing spark-gaps are energized in succession, each preferably several times per second, can achieve a line gradation of over-lapping of shock wave target areas so that each unit volume of the distributed product and the insect infestation therein is thoroughly and repeatedly treated. These actions may also be aided by possible guidance, as by reflection from the walls of the treatment chamber, of the shock waves or components thereof.

As earlier above indicated the treatment zone or chamber Z of Figure l, together with the means indicated diagrammatically at C in Figure l and by which the infested product is supported or carried or guided, all in relation to the shock-wave-producing spark-gap or spark-gaps, may take any suitable form or forms for practicing my mvention according to the principles herein disclosed, and the arrangement shown in Figure 4 and also described above is intended to illustrate one form or embodiment of mechanical features which may be employed in practicing my invention, as for carrying out the method thereof for destroying, by shock waves in air, insect infestation in various products. Other mechanical embodiments of mechanical features may be employed in practicing my method and for purposes of illustration the treatment chamber or zone Z and the means C of Figure l may be embodied in a form such as that shown in I arcano Figure inwhich the element C2 represents a pipe or conduit such as might be used in guiding or moving the product from one factory machine to another or from one part of a machine to another part thereof or whereby the. product to be treated is directly passed on for further processing, such as in the feeding of mired or blended or otherwise prepared cigarette tobacco to the cigarettemaking machine or machines, and for purposes of villustration the pipe C2 of Figure 5 may be considered as a vertical pipe for gravity feed of the productv which'is not indicated in Figure 5 except as the arrow 8l indicates vdirection of movement thereof.

In the pipe C2I mount and align in the direction of product travel the plurality of spark-gaps, illustratively 2 in number, being the spark-gaps G1 and G2 of Figure land comprising the respective spherical electrodes E2-E1 and E2E4; as indicated in Figure 5 the several spark-gaps and their sphere electrodes are aligned on the axis of the feed pipe C2, so that the high-pressure high velocity pulses in air, or shock waves, will have relatively uniform distribution of propagation relative to the circular cross-section of the conduit passage along which the product falls or moves, in the direction of arrow 8l, in more or less uniformly distributed manner.

The conduit C2 is preferably of metal and is preferably grounded as indicated. The several spark-gap electrodes are supported therein so as tobe insulated from the pipe and also to insulate from each other the respective eloctrodes of the several spark-gaps employed.

Thus, sphere electrode E3 may be integrally formed with a conductive L-shaped shank 83 surrounded, except for the sphere electrode itself and a terminal-connecting end of the shank, by a suitable insulating medium such as the insulator 84 made of solid dielectric-material molded thereabout to appropriate thickness and external conformation, substantially as shown in Figure S, whereby it is also insulatingly supported a suitable aperture in the wall of the pipe. In substantially similar manner electrode E4 has an L-shaped conductive shank 85 insulated and supported, in a wall aperture, by insulator 86. Sphere electrodes E1 and E2 at the respective ends of a T-shaped conductive shanlt87 which is surrounded and insulated by the molded insulator 88, for mounting in a wall aperture, substantially as shown. The electrical connections of the terminal-connector ends of the shanks 83, 87 and 85 to bring the spark-gaps G1 and G2 into the circuit and control arrangement of Figure 1 are as diagrammatically indicated in Figure 5, namely, conductor 44 of Figure 1 isconnected to shank 83 of electrode E3 of spark-gap G1 and conductor 52 of Figure 1 is connected to shank 85 of electrode E4 of spark-gap G2 and, since their respective companion elech'odes E1 and E2 are electrically and physically integral with shank 87 of FigureS, only one of the connecting conductors 45 and 53 of Figure 1 need be employed and accordingly, in- Figure 5, I have shown conductor 45 connected to electrode shank 87 along with resistor R3 which, because of the successive or sequential energization of the spark-gaps G1 and G2, can serve for both spark-gap circuits.

The shock-wave-producing spark-gaps G1 and G2 of Figure 5 are thus energizable in repeated sequences such as G1, G2, G1, G2, etc.,` resulting in a pattern of shock wave production aligned generally along the direction of travel or falling or moving of product, and achieving repetitive overlapping of shock wave effects lengthwise can be formed ticles of the the immediate` region of vspark-over;

' 10 inthismanneralso,theshockwave electsmaybeguided or distributed both lengthwise of the pipe C2 land through out the internal cross-section thereof, it being that crosssection that is traversed lengthwise-of the pipe C2 by the moving product.

I prefer t'o make vsuitable provision for preventing parproduct from getting into the spark-gap and. for example, I may make the "r-shaped' shank 87 that carries the electrodes E1 and B2 tubular in form, as indicated at 91 in Figure 5, extending the resultant passageways .through the electrodes E1 and E2 to provide inthe latter discharge openings directed toward the respective companion electrodes El and E4, and supply the tube-passages, as by a hose 92 of insulating material connected to the terminal end of shank 87, with low pressure compressed air from any suitable source, insulating hose 92 being of appropriate length in relation to the operating voltages employed. Each electrode E1 and E2 is thus made to emit av steady tlow of air directed toward and against its companion electrode with the effect that, aided by the expansion and dispersion of the emitted air, each spark-gap is kept free and clearr of product particles and the latter are kept out of and away from the spark-over and the immediate spark-over region between the active electrodes. Pres-A sure and rate of this vair tlowinto the spark-gap regions are of course held at values insucient to detrimentally interfere with suitably free movement'or llow of the product particles along the pipe C2 and past and about the insulator structures of the electrodes.

These insulator structures 84-88 and.86 are preferably metal-covered or metal-coated, as by any suitable metal spraying or surface-metalizing process, throughout their external surfaces as indicated at 90 in Figure 5, leaving uncoated only the relatively small insulating areas of each insulator immediately adjacent and about the protruding sphere electrode and also similar areas, externally of the pipe C2, connector ends of the respective shanks. The metal coating of each insulator is in electrical connection with the grounded metal pipe C2 at the places where the several insulators are fitted and secured in the respective round apertures in the wall of the pipe C2; with the conductive coatings 90 thus grounded, static charges cannot collect thereon and product particles are not attracted or adhered thereto or thereon. It will be noted, in Figure 5, that, with the just vdescribed arrangement, the uncoated areas of the insulators about the respective sphere electrodes thereof are within the immediate regionof the abovel described emitted and expanding air supplied through the hose 92 and by the resultant motion or turbulence of such air detrimental accumulation of piling up of product particles thereon does not take p ace.

In the arrangement of Figure 5 the substantially total enclosure of the shock-wave-producing spark-gap or sparkequipment. In the arrangement of Figure 4 the hood-like of the direction of travel of the product as its passes through the region adjacent' and about the first spark-gap, being spark-gap G1 in Figure 5, and as it passes through the region adjacent and about the second spark-gap, being spark-gap G2 in Figure 5. Moreover, the conduit or pipe C2.can act as a guide for the shock waves, leading or guiding them lengthwise of and along the interior of the tube or pipe C2 and the interior walls of the latter may also ooact by reilective action on the shock waves;

structure 14 can also be made of metaland grounded as indicated and can take .part in similar shielding or suppression action.

The shock-wave-producing spark-gap or spark-gaps are preferably, according to certain features of my invention, fast gaps in that spark-over is not preceded by corona and accordingly I make the electrodes spherical as above described, with appropriatespacings therebetween in relation to the sphere diameter. For example, where the voltage applied is 40,000 volts, the diameter of the sphere electrodes can be about two inches and the spacing or gap therebetween about 0.400 inch. Where the spark-gap electrodes have bare shanks, as indicated in the arrangeadiacent-and about the terminal v l1 ment bf Figure 4. known proportioning of shank diameters to sphere diameters is resorted to to insure that sparkover or discharge does not occur between the supporting shanks of the sphere electrodes, and the shanks of the electrodes of each gap are preferably not parallel to each other; thus as indicated in Figure 4, while the shank of electrode E1 of gap Ga may be supported in the insulating support 12 with its axis substantially vertical, the shank of companion electrode Ea is supported so that it makes a substantial angle to the shank of electrode El, in the manner indicated in Figure 4. In similar manner the shank of electrode E* of gap Gz is supported at a substantial angle to the shank of its companion electrode E. Such arrangement, where the sphere electrodes have bare shanks, co-acts to prevent corona discharge preceding the spark-over. The fast gaps, upon sparkover, thus achieve sudden rupture through the air between their respective electrodes and substantially` concurrent and sudden conversion of the energy'of the spark-over into a discontinuity in air that ernanates from the immediate region of spark-over and is propagated therefrom at high velocity, a velocity that can be several times the local velocity of sound; the fast spark-gap or gaps co-act in dependably achieving high rate of energy input into the spark, thus facilitating the production, for each spark-over, of a shock front of the desired energy content and velocity for achieving destruction of forms of insect life in the product. This velocity may be from just below sonic velocity to several times the local velocity of sound, and any suitable means may be employed to correspondingly CFI set or adjust the electrical energy input to the spark-gap or gaps; for example, and as above already indicated, the current pulses supplied to each spark-gap may be adjusted to desired values by correspondingly setting the conductivity of the magnetrons, as by controlling filament temperature by the variable resistances 40 and 41 for thc magnetrons Ml and M2.

vAs above noted, the pressure pulse or shock wave emanates from the immediate region of spark-over at a velocity that can be several times the local velocity of sound, and as it travels away from the region of sparkover where it originated, there is some loss in its velocity as its distance of travel increases but the rate of velocity diminution becomes very low as it nears the local velocity of sound. Accordingly the shock waves have substantial range before they reach sonic velocity and still greater range before they reach values just below sonic velocity, and it is within such ranges that the infested product is subjected or brought to the spark-gap or spark-gaps for destruction of the forms of insect life in the product. Desirably the infested product is brought as closely as possible to the region of spark-over to gain the benefit of the higher instantaneous values of velocity of the shock wave and of the correspondingly greater energy of impact thereof with the forms of insect life; but even where the forms of insectlife in the product are encountered by shock waves, within the above-mentioned range of velocities, that are of lesser velocity of travel, there is repetitive or multiple impacting thereof by the successive shock waves produced by the succession of spark-overs, including the above vdescribed repetitive sequences of shock waves from a plurality of spark-gaps, and the resultant cumulative shock wave effects coact to produce lethal effects on the forms of insect life.

`Illustratively, a fast gap with sphere electrodes about two inches in diameter, having a gap therebetween of about 0.400 inch, may be energized from a capacitor of 0.5 microfarad charged at 40,000 volts, as in the circuit Figure l; Vthe belt Cl of Figure 4 may have a width of about l2 inches, and the conveyed product, such as moist cigarette tobacco, dried fruit suchras raisins, or dried products such as dried beans, may have its particles or components spread thereon in a layer about l inch thick with a spacing between the supporting surface of the belt 12 and the axis of the sphere electrodes on theorder of 3 inches or so. Belt travel may be on the order of 5 inches per second and in Arelation thereto, as by selecting the desired speed by selector control 64 (Figure l), the timer-distributor D may be given a speed of 2 R. P. S. which provides a pulse repetition rate of 4 per second; with a pulse duration of, say, micro-seconds, pulse energy is on the order of 250` joules, and consequently energy is transformed in the gaps at the rate of about l kilowatt per hour. Such data as these illustratethe high order of magnitude of electrical energy that it is possible to make available, and at a high rate of input, in the spark-over for conversion into usable shock waves Afor lethal effects upon forms of insect life in infested products of the above-mentioned nature; it will be understood that these data are set forth only in an illustrative and not in a limiting sense. For example, electrical constants of the illustrative circuit of Figure l may be, in known manner, varied or changed or made variable to provide other values and rates of electrical energy input to the fast gap or gaps for the production of shock fronts or shock waves lethal to such forms of insect life. Likewise, spacings of the product from the fast-gap electrodes and depth of layer thereof on the belt may be changed as earlier above described in relation to speed of the belt and to pulse repetition to suit etective shock-wave intensity to `'characteristics of the product and its infestation.

As described above, Figure 4 shows a plurality of shock-waveproducing spark-gaps aligned generally crosswisc of the'path oftravel of the product to be treated while Figure 5 shows them aligned generally lengthwise of the travel of the product, each with appropriate sequential shock-wave-producing energization of the spark-gaps. As also noted above, other geometric patterns of spark-gap arrangement for sequential shock wave production may be utilized in the practice of my invention and Figure ti illustrates one such other arrangement diagrammatically. Also, from the above descriptions of Figures 4 and 5, it will now be apparent that, in Figure 4, electrodes E1 and E.I of the spark-gaps G1 and G2 can be connected into the circuit through a single conductor 45 las are the electrodes El and Ez of Figure 5. Also, and as shown in Figure 6, a singlesphere electrode can be common to several gaps; lthus electrode El is shown as companion to electrodes E3 and E* to either side of it, forming the two fast gaps G1 and (i3 arranged transversely of the distributed product carried by belt C1 and sequentially energized as described above, particularly in connection with Figure 5 so far as the circuit connections are concerned. Adjacent gaps Gl and GI as in Figure 6, I may provide additional ones such as fast gaps G3 and G4 that comprise paired sphere electrodes Ex and EY, all grouped appropriately in relation to the product distribution or travel. The circuit arrangement of Figure l, supplied with additional magnetrons for gaps G3 and G4, and with two additional brushes on' the timer-distributor D and corresponding current'interrupters to coact therewith, the four currentinterrupters being. space'90, in the manner earlier above described, can provide the desired sequence of energie tion of the shock-waveproducing gaps, for example, in the order G, G3, Gf', G1, G4, G3, ete. with a corresponding and, in this case, rotatively-travelling pattern of stlck wave production relative to the product being When the apparatus is shut down, switch 33 (Faire 1) is closed to discharge capacitor 20 through a suitable resistance 29.

It will thus be seen that there has been provided in this invention a method for treating insect-infested products, such as cigarette tobacco, by shock waves for the destruction of such insect life in its various forms or stages, together with a system and apparatus for so treating such insect-infested. products, all readily adaptable to meet varying practical requirements or conditions,

'l I3 t including facility and economy of association with or corporation into a production line ment or machinery operating inthe latter. l Moreover, it will be seen that the several objects above noted or indicated,` together with many thoroughly practical advantages, are successfully achieved. `The method'and system are characterized by facile control and flexibility for corelating various elements and their coactions in relation to'each other and to practical operating requirements, such as has been illustratively set forth above.

'I'his application is a continuation-impart of my application Serial No. 129,655, tiled November 26, 1949, now matured as U. S. Patent No. 2,664,850 issued January 5, 1954.

As many possible embodiments may be made of the mechanical features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinabove set forth, or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

l. A method of destroying insect life in an infested product which comprises Supplying electric current of sucient intensity to spark-over an air gap, interrupting said current at predetermined intervals of time to generate a plurality of separate intense current pulses in the'gap to form a plurality of separate shock waves in air which radiate out from the path of travelof the intense cu-rrent pulses across the gap at a velocity in the range just below the local velocity of sound to several times the local velocity of sound and then moving the product in bulk in a path exterior to and not intersecting the path of the intense current pulses across the gap but intersecting the path of the shock waves radiating out from the current pulses to destroy insect life in the product.

2. A method as specified in claim 1 which includes the step of moving the product to be treated exterior to and in a direction substantially parallel to the path ofthe intense current pulses across the gap to intersect the v shock waves radiating out from the path of the intense y current pulses across the gap.

3. A method as specified in claim l which includes the step of supplying a stream of a gaseous medium which is directed along the path of the intense current pulses across the gap to provide a barrier substantially preventing entry of product into the path of such intense current pulses.

4. In a method of destroying forms of insect life, by shock waves, in an infested product such as cigarette tobacco, the steps which comprise converting electrical energy into a succession of shock waves in air by repeatedly energizing, at intense current pulses, a fast sparkgap to generate, at each spark-over between the electrodes thereof, and to propagate therefrom, a discontinuity in air of a velocity in the range from just below the local velocity of sound to several times the local velocity of sound, distributing the particles of the infested product on to the supporting surface of a movable carrier, and moving the supporting surface, with the product particles thereon, along a path spaced downwardly from the spark-gap by a distance not greater than the range of travel of the propagated discontinuity and greater than the depth of the product particles onv the supporting surface to prevent product particles from passing into the immediate region of spark-'overbetween the electrodes.

5. Apparatus for destroying insect life in an infested product which comprises at least two electrodes with ya gap between the electrodes for spark-over, means for supplying a dow of electric current to the electrodes of suicient intensity to spark-over the gap, means for interrupting the ow of electric current to generate a plurality of separate intense current pulsesv in the gap to form a succession of separate shock waves which radiate acrossthe 14" outwardlyfrom the path of travel of the inteoeecurtent 4 gap at. avelocity-in the rangeziustfbelow the local velocity of Q0.- several .of sound and meansfor movin'ginfestedproduct-partieles in builtin a path exterior to notintersectingthe path of the intense current but intersecting the path of the shock waves out from such current 6. Apparatus for destroying insee: life an infested product which comprises at least-two fast spark gap electrodes with a gap. between the electrodes for spark-over, means forvsupplying electric current to the electrodes of sutiicient intensity to spark over the gap, means for interrupting the ow of velectriccu'rrent to generate a plurality of separate' intense current pulses in the gap to form a succession of separate shock waves which radiate out in nonparallel direction from the path of travel of the intense current pulses across thegap at a velocity greater than the local velocity of sound and means fory moving the product in a path exterior to and in a direction substantially parallel to the path of the intense current pulses across the gap to intersect the shock waves radiating out from the path of the intense current pulses across the gap and destroy insect life in the product.

7. Apparatusas specified in claim 5' in which the means for interrupting the flow of electric current includes high voltage switching means and low voltage means operating in recurring sequence to control said high voltage switching means and means for controlling the low voltage control means to determine therate of sequential recurrence relative to the rate of movement of the infested product along said path.

8. Apparatusfor destroying insectlife in4 an infested product which comprises means supplying electric current of sucient intensity to sparkfover an air gap, means for interrupting saidy currentA at pre-determinate intervals ot time adapted to generate a plurality of separate intense currcnt pulses in the gap 4to form a plurality of separate shock waves in air which radiate out from the path of travel `of the intense current pulses across the gap and means for moving -the product in bulk in a path exteriorto and `not intersectingthe path of the intense current pulses across the gap, but intersecting the path of the shock waves radiating outwardly from' the current pulses to destroyinsect-life in the product. y

9. Apparatus for destroying insect life in an infested lproduct which comprises a plurality of fast spark gap electrodes arranged in pairs with a spark gap bctween the two electrodes of each pair forv spark-over, means for supplying electric current to the electrodes of suicient intensity to spark-overl the gaps, means for interrupting the iiow of electric current to generate a plurality of separate intense current pulses across the gaps to form a plurality of separate shock waves across each gap which radiate outwardly from the path of travel of the intense current pulses across the gaps at a velocity greater than the local velocity of sound and means for moving infested product in bulk in a path exterior to and not intersecting the path of the intense current pulses across the gaps, but intersecting the path of the shock waves radiating outwardly from the current pulses to destroy insect life in the product.

10. An apparatus as specified in claim 5 in which said means for eEecting movement of the particles of the infested product comprises a movable conveyor which provides a product-carrying surfacev spaced underneath said fast gap electrodes by a distance not greater than the range of propagation of said discontinuity propagated by said spark-over and greater than the depth of the product particles on said supporting surface for thereby preventing the path of movement of product particles from intersecting the immediate region of spark-over between said electrodes.

ll. An apparatus as specified invclaim 5 in which said means for effecting movement of the particles of the in- 15 hated product along the aforesaid path comprises also means for supplying to the immediate sparkover region between said electrodes a stream of air the movement d which, along said regionconstitutes a barrier to the entry of product particles into the immediate region of spark-over.

l2. An apparatus as specied in-claim in which said means for eiecting movement of the particles of the infested product comprises a guiding conduit for the product, with means insulatingly supporting said fast gap electrodes interiorly of said conduit and spaced from the walls thereof, means forming an air passage from the exterior of said conduit to the immediate region of spark-over between said electrodes, and means for supplying a gaseous medium under pressure to said air passage for discharge into said medium region of sparkover between said electrodes and thereby constituting g' barrier against the entry of product particles into said region.

13.l An apparatus as specilied in claim 5 in which said means for etecting movement of the particles of the intested product comprises a guiding conduit for the product, with means insul-atingly supporting said fast gap electrodes interiorly of said conduit and spaced from` the walls thereof, one of said electrodes having an orificelike discharge opening directed toward the other electrode at the region of electrical spark-over therebetween, and means for supplying a gaseous medium for discharge thereof from said discharge opening at a velocity insucient to detrimentally affect spark-over between the electrodes and suliicient to maintain, substantially -about said region of spark-over, a barrier against the entry of product particles into the spark-over region.

14. An apparatus as specified in claim 5 in which said means for electing movement of the particles of the infested product comprises a guiding conduit for the product, with means insulatingly supporting said fast gap electrodes interiorly of said conduit and spaced from the walls thereof, and means constituting a barrier about the region of spark-over between said electrodes for preventing product particles from entering said region.

l5. An apparatus as specified in claim S in which said means for effecting movement of the particles of the infested product comprises a guiding conduit for the product,' with means insulatingly supporting said fast gap electrodes interiorly of said conduit and spaced from the wails thereof, with grounded conductive means associated with surface portions of said means for insulatingly supporting said electrodes and thereby lead off static charges ukvlhich would otherwise cause product particles to adhere t ereto.

16. An apparatus -as specied in claim 15 in which said conduit is electrically conductive, with means for grounding it, said conductive means being in electrical connection with said conduit. p

17. An apparatus as specied in claim 6 which includes insulating means for supporting said electrodes to position the electrodes with the path of spark-over in the fast spark gap generally transversely of said' path of movement of the infested product particles with the effective transverse spacing between adjacent fast sparkgaps not greater than that at which the sum of the transverse dimensions of the target areas of the respective shock waves is less than the transverse dimension of the path of movement of the infested product particles.

18. An apparatus as speciled in claim 6 which includes a conveyor belt for moving the particles of infested product along said path and which includes means for insulatingly supporting the electrodes of the fast gaps in distributed relation overlying the conveyor belt and supporting at least some of the fast gaps distributed generally transversely ofthe conveyor belt.

References Cited in the tile of this patent OTHER REFERENCES Carlin, B. U1trasonics, page 27, published 1949 Vby McGraw-Hill Book Co., New York.

A Text-book of Soun by A. B. Wood, page 218, published 1946 by Bell and Sons, Ltd., London. 

